In most drunk driving cases in Oakland County, officers will administer a preliminary breath test on the side of the road prior to arresting somebody suspected of drinking and driving. This test is for the most part prohibited from being used at trial and its sole purpose in obtaining the test is so the officer can create probable cause to arrest.
Many times we see that the preliminary breath test, or PBT, gives a different blood alcohol level than the subsequent Datamaster or blood test. There are trials in which we have been successful in actually admitting the PBT to show the difference between the scores of the various tests. This is especially helpful if the PBT is much lower than the subsequent alcohol test.
There are also times you can challenge the validity of the arrest if the PBT was not administered properly. PBT administration is governed by the Administrative Rules and are promulgated by the State Police. Rules such as the officer establishing that the suspect has not placed anything in their mouth, regurgitated, or smoked with the fifteen minutes prior to the taking of the test come into play when arguing that the officer lacked the probable cause to arrest.